Hard surfacing material



H. c. BRIDWELL ETAL 3,128,165

April 7, 1964 HARD SURFACING MATERIAL 2 Sheets-Sheet 1 Filed Nov. 15, 1961 FIG FIG. 2

HAROLD c. BRIDWELL DAVID s. ROWLEY INVENTORS ATTORNEY April 1964 H. c. BRIDWELL ETAL 3,128,165

HARD SURFACING MATERIAL Filed Nov. 15, 1961 2 Sheets-Sheet 2 FIG 3 HAR OLD c. BRIDWELL DAVlD S. ROWLEY INVENTORS ATTORNEY United States Patent lice 3,128,165 HARD SURFACDIG MATERIAL Harold C. Bridwell and David S. Rowley, Tulsa, 0l la., assignors to Jersey Production Research Company, a corporation of Delaware Filed Nov. 15, 1961, Ser. No. 153,257 Claims. (Cl. 51-307) The present invention relates to materials for hard surfacing bits and similar cutting tools and more particularly relates to an improved hard surfacing marterial containing cutting elements of hard metal carbide supported by a matrix of softer metal within which crystals of hard metal carbide have been precipitated.

Particles of tungsten. carbide or tungsten carbide alloy supported in a matrix of softer metal are \widely used as cutting elements on rotary drill bits and tools. Such particles may be applied by placing the tool to be hard surfaced in a refractory mold, positioning the carbide particles in the mold in contact with the tool surface, adding pellets of the matrix metal, and then heating the mold and its contents in an electric furnace to a temperature sufficient to melt the pellets. The molten matrix metal infiltrates into the spaces between the particles and the tool surface, effecting a bond as it cools and solidifies. Metals used in this manner must have the ability to wet the carbide particles and steel and must have melting points well below the temperature at which properties of the carbide are adversely affected. These requirements restrict the selection of matrix materials to metals which inherently have low strength and little resistance to wear and abrasion. Such metals are unable to withstand the severe stresses to which drill bits and similar cutting tools are normally subjected and are therefore .wo-rn away at a relatively rapid rate. Failure of the matrix leaves the carbide cutting elements partially unsupported, causing them to fracture or be torn from place prematurely. As a result, the useful life of drill bits and similar tools hard surfaced with such materials is usually short.

it is therefore an object of the present invention to provide an improved hard surfacing material containing hard metal carbide cutting elements which has greater strength than materials available in the past. A further object is to provide a process for the manufacture of a hard surfacing material having a matrix capable of supporting hard metal carbide cutting elements under adverse conditions for long periods of time. Other objects will become apparent as the invention is described in greater detail.

In accordance with the present invention, it has now been found that improved hard surfacing materials containing hard metal carbide cutting elements supported in a matrix of softer metal can be prepared by infiltrating the particles with the matrix met-a1 under conditions such that metal carbide crystals are precipitated in the matrix as a discontinuous phase. Metallurgical studies have shown that the precipitated crystals interrupt the slip and glide planes in the infi'ltrant metal, permitting the matrix to withstand higher stresses without fracturing than if the crystals were not present. This is reflected by an increase in the strength of the matrix. As a result, the hard metal carbide cutting elements are better supported and have less tendency to fracture and be torn from place than those in hard surfacing materials available in the past.

The hard metal carbide crystals responsible for the improved matrix properties are provided by dissolving powdered metal carbide in the molten matrix so that it will precipitate as the matrix cools following infiltration. The powdered carbide may be dissolved in the 3,128,165 Patented Apr. 7, lgfid matrix met-a1 prior to the infiltration step or may instead be placed in the mold with the hard metal carbide cutting elements and at least partially dissolved as the hot matrix metal infiltrates into the spaces between the cutting elements. In either case, carbide crystals are precipitated in the matrix as the metal cools and solidifies. It is usually preferred to include the powdered carbide in the mold. Studies have shown that finely divided carbide powder cont-acted by the flowing matrix metal at high temperature is altered in structure even though it may not be completely dissolved and subsequently precipitated in crystalline form. The presence of these altered carbide powder grains and precipitated crystals generally results in a harder, stronger matrix than can be obtained by dissolving the powder in the matrix prior to infiltration.

The invention can be better understood by referring to the following description of the process employed to prepare the improved hard surfacing material and to the accompanying drawing, in which:

FIGURE 1 represents a vertical section through a mold used for infiltrating metal carbide cutting elements with a matrix metal to produce the hard surfacing material of the invention;

FIGURE 2 depicts a cross section taken about the line 22 in FIGURE 1; and,

FIGURE 3 is a reproduction of a photorniorograph showing the matrix structure of the improved hard surfacing material.

The infiltration process utilized to produce the hard surfacing material of the invention is carried out in a refractory mold similar to that shown in FIGURE 1 of the drawing. The mold depicted includes a lower section 11 provided with threads 12 for attaching an upper section or cover 13. The lower section contains a recess within which the hard metal cutting elements and the tool or part to which they are to be bonded may be placed. The shape of the recess will depend upon the desired configuration of the finished tool. It should be designed to accommodate the tool with the surfaces to be hard surfaced facing upwardly. Sufficient space must be left adjacent these surfaces to permit addition of the carbide cutting elements. It is generally preferred to machine a large recess in the lower section of the mold and then insert spacers 14 of refractory material to obtain a recess of the proper shape. The space-rs employed are shown more clearly in FIGURE 2 of the drawing. Strips of clay, sand or similar material 15 may be placed between the spacers and wall of the mold on two sides of the recess to fill the voids and permit thermal expansion as the mold contents are heated. The upper section of the mold contains a depression 16 and ports 17 extending through it. The mold parts may be made of carbon or a refractory ceramic material. The use of a carbon mold is preferred because of the ease with which carbon blocks can be machined.

After a suitable mold has been prepared, it is thoroughly cleaned to remove water, grease and other foreign materials. If a carbon mold is utilized, the mold recess may be lined with Fiberfrax or :a similar asbestos material at points where the metal tool or part to be hard surfaced would otherwise contact the carbon. This prevents carburization of the tool steel at the temperatures required for infiltration. The tool or part 18 is then placed in the mold and the hard metal carbide cutting elements 19' are added. Both the tool and the carbide cutting elements should be cleaned with carbon tetrachloride or a similar solvent to remove dirt, grease and other foreign materials before they are placed in the mold.

The carbide particles employed as cutting elements may be particles of tungsten carbide or particles of a mixed carbide including small amounts of titanium carbide, tantalum carbide, niobium carbide and other metals in addition to the tungsten carbide. Such carbides are available in either cast or cemented form. The cemented carbides normally contain from about 1 percent to about 25 percent of cobalt or a cobalt alloy containing a small amount of iron or nickel. emented carbides, particularly cemented tungsten carbide containing from about 3 to about 15 weight percent cobalt, are preferred because they are generally less brittle than the cast carbides and are therefore better suited for use as cutting elements. The size of the cutting elements employed will normally range between about 0.045 inch and about 0.400 inch along their major dimension. For rotary drag bits and similar tools, particles between about 0.050 inch and about 0.250 inch are generally used. Carbide particles of suitable size are commercially available in various forms. Angular chips produced by fracturing large pieces of carbide will normally be used but in some cases particles of regular shape, cubes for example, are preferred.

The hard metal carbide cutting elements are generally packed into the mold voids as closely as possible in order to provide a maximum number of cutting edges on the tool surfaces. If cubes or similar shaped particles are used, however, it may be desirable to orient the outer layer by gluing or otherwise afiixing particles to the mold or mold inserts. Subsequent infiltration of matrix metal into the space surrounding the oriented particles will result in their being bonded in place. Diamonds may be mounted in similar manner in order to augment the cutting action or reduce wear at critical points on the tool.

As pointed out previously, powdered hard metal carbide is preferably placed in the mold cavity with the hard metal cutting elements in applying the hard surfacing material. The composition of the powdered carbide thus used may bee identical to that in the cutting elements. Instead, a powdered carbide having somewhat different properties, one which is harder but more brittle for example, may be employed. Tungsten carbide and mixed carbides containing tungsten carbide, titanium carbide, tantalum carbide, niobbium carbide and other metals are suitable. To promote rapid solution of the powdered carbide in the matrix, a fine powder should be used. Powder which has been screened to pass a 100 mesh or small Tyler screen may be utilized. It is preferred to employ powder of 170 meseh or smaller size. From about 5 to about 35 weight percent powdered nickel will preferably be included with the powdered carbide to promote wetting of the carbide by the infiltrant matrix metal. The nickel used should be ground and screened in a manner similar to that in which the powdered carbide is prepared. A small amount of powdered tungsten may also be included to further increase strength and hardness. The powder should be cleaned to remove moisture, dirt and grease. The mold will normally be cold pressed or vibrated as the powder and cutting elements are added in order to form a dense, closely-packed mass in the voids adjacent the tool surface. After the mold has been carefully filled with the carbide powder and cutting elements, the mold cover 12 is threaded onto lower section 11 and tightened down. The mold may be placed in a press to assist in tightening the cover in place.

The relative amounts of the carbide cutting elements and powder used in packing the mold may be varied over a wide range and will depend in part upon the size of the cutting elements. Where cutting elements about inch in size are used, for example, the cutting elements will generally constitute about 50% of the total volume of the hard surfacing material. If larger particles are employed, the portion of the total volume occupied by cutting elements may be somewhat smaller.

Following assembly of the mold, pellets or similar particles of matrix metal 20 are placed in recess 16 in the mold cover. The metal employed to form the matrix should be capable of wetting the hard metal carbide in the molten state and should have a melting point between about 1550 F. and about 2400 F. Suitable metals include copper-nickel alloys, copper-nickel-tin alloys, copper-nickel-iron alloys, nickel-iron-carbon alloys, coppercobalt-tin alloys, copper-nickel-iron-tin alloys, coppernickel-manganese alloys and the like. Such alloys may contain minor amounts of other metals such as zinc, manganese, silicon, silver, beryllium, bismuth, boron, cadmium, chromium and phosphorus. S Monel and a number of other commercially available brazing metals and similar alloys which melt within the above specified temperature range and will wet the carbide and steel may be utilized for purposes of the invention. It will be understood, of course, that every alloy has slightly different properties and that certain alloys are therefore more effective for purposes of the invention than are others. The use of copper-nickel-tin alloys is preferred. A small amount of borax or other flux is added to the pellets in the mold cover to aid in the control of oxide formation during the formation of the hard surfacing material.

The assembled mold containing the tool to be hard surfaced, the carbide cutting elements, powdered carbide, and pellets of matrix metal is placed in a furnace previously heated to a temperature sufficient to melt the matrix metal. The temperature utilized should be well below the temperatures at which properties of the carbine employed are adversely affected. The furnace temperature will depend somewhat on the matrix metal and powder used but will generally range between about 1750 F. and about 2500 F. The temperature used should not greatly exceed that required for rapid infiltration of the matrix metal into the carbide particles and powder. The composition of the matrix metal and powder in the mold will govern the infiltration temperature. Copper-nickel alloys will readily infiltrate at temperatures between about 2000" F. and about 2250 F, for example; whereas slightly higher temperatures are required for the infiltration of ironnickel-ca-rbon alloys and the like. The mold is left in the furnace for a sufficient period of time to permit its contents to reach the furnace temperature. The pellets of matrix metal in recess 16 in the mold cover 13 melt at the elevated temperature and flow downwardly into the mold through ports 17. Capillary forces cause the hot molten metal to infiltrate into the interstices between the carbide cutting elements, carbide powder and surface of the tool. The powdered carbine is altered in structure and is at least partially dissolved by the infiltrating metal. After sufiicient time for the mold contents to reach the furnace temperature and for infiltration to occur has elapsed, normally from about 4 to about 30 minutes, the mold is removed from the furnace and is allowed to cool. As the matrix metal cools and solidifies in the mold, fine crystals of the previously dissolved metal carbide powder are precipitated in it. The tool may be removed from the mold after it has reached room temperature and may be subjected to conventional heat treating procedures in order to relieve thermal stresses set up in the steel during the infiltration process. Thereafter, the tool may be sand blasted and machined or ground to remove surface irregularities. The finished tool will have a hard surface of metal carbide cutting elements securely supported by a softer matrix containing a discontinuous phase of fine hard metal carbide crystals.

In lieu of placing the powdered hard metal carbide in the mold with the carbide cutting elements as described above, carbide powder may be dissolved in the matrix metal prior to infiltration. The pellets of matrix metal may be placed in a clay crucible or other vessel of refractory material with a small amount of borax or other flux and heated to the melting point. Powdered metal carbide may then be added to the molten metal in quan tities sumcient to saturate it. Inclusion of the carbide powder may produce some elevation in the melting point of the matrix metal. If it is found that the melting point of the final alloy is greater than about 2400 F., it can be adjusted downwardly by realloying the metal with copper, tin or similar metal until the desired melting point is attained. The final alloy may therefore be undersaturated in terms of its metal carbide content but will nevertheless contain sufiicient hard metal carbide to effect a significant increase in strength as the matrix cools following infiltration and the carbide precipitates in crystalline form. The matrix metal thus prepared by predissolving the carbide powder in the molten metal may be solidified and formed into pellets or fragments of suitable size. Thereafter, it can be employed for infiltration purposes in a manner similar to that described earlier.

The method of the invention is not limited to the direct bonding of hard metal carbide cutting elements as described above and may instead be employed for the production of pads or inserts to be subsequently bonded to a tool or similar device. In the making of such pads or inserts, the carbide cutting elements are placed in a mold of the desired shape and bonded together by infiltration with the molten matrix. Hard metal carbide powder may either be predissolved in the matrix or may be included in the mold with the carbide cutting elements. The pad or insert thus formed may then be applied to a steel surface by brazing. Pads or inserts may also be formed on small steel plates by infiltration and later affixed to a tool or other device by welding the plates in place. These methods are useful for the hard surfacing of large areas with the hard surfacing material of the invention.

The superior properties of the material of the invention are illustrated by the results of experimental work designed to test the effect of precipitated carbide crystals upon the matrix strength of hard surfacing materials containing metal carbide cutting elements.

In a first series of tests, specimens containing tungsten carbide cutting elements supported by a copper-nickel-tin alloy matrix were prepared. The tungsten carbide cutting elements employed were angular fragments of cemented tungsten carbide containing 90.0 weight percent of tungsten carbide and 10.0 weight percent of cobalt. The hardness of these fragments ranged between 88.8 and 89.0 on the Rockwell A scale. The particles were screened to remove fragments smaller than about 0.12 inch and greater than about 0.20 inch. The screened fragments were then washed with alcohol to remove grease and other foreign material and were dried with an air blast. The dried fragments were placed in clean, dry carbon molds containing cylindrical voids /2 inch in diameter by 1 inch long. In some cases powdered tungsten carbide and powdered nickel were mixed and added to the mold with the carbide cutting elements; while in others no powder was used. The molds were then infiltrated with a molten matrix metal containing about 35 weight percent copper, about 5-5 weight percent nickel and about weight percent tin at a temperature of 2250 F. Following infiltration, the molds were removed from the furnace and cooled. In each case, the total furnace time was minutes.

The specimens prepared as described above were examined under a microscope. It was found that the matrices of those prepared with the carbide powder contained fine crystals of precipitated tungsten carbide. FIGURE 3 of the drawing is a reproduction of a photomicrograph of a matrix prepared with carbide powder, taken at 50 0 power magnification. The crystals in the matrix are clearly visible in the photomicrograph and appear in most cases as elongated, angular bodies. The cluster of smaller particles in the lower right quadrant of the photomicrograph is all that remains of a grain of the carbide powder altered by the hot matrix metal. These precipitated crystals and altered powder grains interrupt the slip and glide planes of the matrix metal and are largely responsible for the improved matrix properties of the hard surfacing materials of the invention.

Following microscopic examination of the matrix structures, the mechanical properties of the specimens were determined. Compressive strengths were measured by first grinding specimens so that their ends were flat and parallel and then testing them on standard Baldwin and Olson test machines. There was little displacement of any of the specimens prior to fracturing. The fracture angles in most cases were about 5 degrees to about 25 degrees from the load axis. -It was found that the compressive strengths of the specimens containing the precipitated crystals were about twice those of the specimens prepared without powdered carbide.

The shear strengths of the specimens were measured by placing them in adapters which permitted the application of force in opposite directions on either side of a plane perpendicular to the specimen axis. The shear fractures obtained were granular in appearance and extended parallel to the load axis. Cemented carbide cutting elements in the specimens sheared in the plane of matrix fractures. Two fractures commonly occurred, producing a disc-like fragment at the center of the specimen. The second of these fractures was apparently due to tension failure caused by slight bending of the specimen after shearing forces had started the first fracture. The shear strengths of the specimens containing the precipitated crystals were substantially higher than those of specimens prepared without the powdered carbide.

Impact tests were carried out by placing the cylindrical half inch by one inch specimens in a specially designed holder and striking them with a special striker on a standard Charpy impact testing machine. The specimens prepared in accordance with the invention had significantly higher impact strength than the other speclmens.

The data referred to above are summarized in the following table. A number of specimens of each material were prepared and tested to obtain the data and hence each of the values given in the table represents an average of at least two tests. The differences between the indi vidual values on which the averages are based were small.

TABLE I All specimens prepared by infiltrating angular cemented tungsten carbide fragment screened to about 0.12 to about 0.20 inch size with alloy containing about 35% copper, about 55% nickel and about 10% tin at 2250 F.; furnace time was 15 minutes in all cases.

The data in Table I above show that specimen B which was prepared in accordance with the invention had much greater strength than did the other specimens. The compressive strength, shear strength and impact strength were all much higher due to the presence of the carbide crystals and altered carbide powder. These improved properties make the material of the invention much more resistant to wear and abrasion than materials available heretofore.

The importance of utilizing very fine powdered hard metal carbide is also shown in Table I. Specimen C, in which relatively coarse 28-35 mesh carbide was used, was only slightly better than. specimen A which was prepared without powdered carbide. Little of the coarse carbide dissolved in the molten matrix under the conditions employed; whereas the finer powder used in specimen B dissolved in substantial quantities and was subsequently precipitated in crystalline form. The use of powdered carbide ground to pass a 100 mesh or smaller screen is therefore important in preparing the material of the invention.

Addtional experiments similar to those described above were carried out to determine the effect of variations in the composition of the matrix metal upon the properties of the improved hard surfacing material. Test specimens were prepared by infiltrating tungsten carbide cutting elements and a minus 170 mesh mixture of 83 weight percent tungsten carbide powder and 17 weight percent nickel powder with three different matrix alloys. The first of these alloys was the copper, nickel and tin alloy described earlier. The second was an alloy containing 67 percent nickel, 30 percent copper, 1.4 percent iron, 1 percent manganese and trace quantities of other metals. The third was an iron-nickel alloy containing about 90 percent iron and about percent nickel. These alloys all melted at temperatures between about 1550 and about 2400" F. The first was used at an infiltration temperature of r2250 F., while the latter two were used at a temperature of 2350" F. because of their higher melting points. The infiltration procedure employed was similar to that described earlier. Specimens of the alloys alone were also prepared. The specimens were tested to determine their compressive strength, shear strength and impact strength. The results of the tests are set forth in Table 11 below.

TABLE II Comparison of Matrix Alloys Shear Strength, p.s.i.

Compressive Strength,

p.s.i.

Impact Strength, lb.-1t.

Specimen 1 Each value represents an average of at least two tests.

It will be seen from Table II that the improved properties obtained in accordance with the invention are not limited to materials containing the cupronickel alloy referred to in connection with Table I and that iron-nickel alloys and similar matrix metals may also be employed. The compressive and shear strength values for the specimens prepared with tungsten carbide cutting elements and mixed tungsten carbide-nickel powder were much higher than those obtained for the specimens containing only the alloys. Although the carbide cutting elements may have contributed slightly to the greater strength obtained, the improved properties were due primarily to the inclusion of the powdered carbide. The efiect of the carbide powder on impact strength was offset in some of the specimens by the efiect of the relatively brittle cutting elements and the impact data on Table II reflect this. In the case of the iron alloy matrix, however, the inclusion of the powdered carbide produced a significant increase in impact strength.

Still other experiments were carried out to further demonstrate the importance of dissolving and reprecipitating the powdered carbide. Specimens were prepared by infiltrating cemented tungsten carbide fragments and minus 170 mesh tungsten carbide-nickel powder with the copper, nickel and tin alloy referred to in connection with the earlier tests. The compositions of the cemented carbide fragments and the mixed powder were the same in all cases. Furnace times were varied from five minutes to $5 One hour. The prepared specimens were then tested to determine their compressive strengths as described previously. The results obtained are shown in Table III.

TABLE III Efiect of Furnace Time Upon Matrix Strength Composition furnace Compressive timeMinutes: Strength, p.s.i. 5 188,250 10 222,500 15 210,510 30 227,830 60 228,000

' WC-10% Co cutting elements plus 170 mesh mixture of 85% WC-17% Ni powder infiltrated with an alloy containing about 35% Cu, 55% Ni and 10% S11 at 2250 F.

The data in Table III above demonstrate that the compressive strength of the matrix tends to increase with increased furnace time. The longer the molten matrix metal remains in contact with the powdered carbide, the more carbide is dissolved and subsequently precipitated in crystalline form upon cooling of the matrix. Since carbide solubility is also a function of powder size and matrix temperature, however, the use of extended furnace time is not essential. This is particularly true where the powdered carbide is predissolved in the molten matrix metal.

The superior properties of the materials of the invention are further illustrated by the results obtained in drilling tests carried out with two oil field rotary drag bits of similar design. The blades of the first bit were hard surfaced with a copper-nickel matrix containing angular particles of cemented tungsten carbide between about A; and about /8 inch in size. The matrix contained no altered tungsten carbide powder or precipitated tungsten carbide crystals. The blades of the second bit were hard surfaced by infiltrating cemented tungsten carbide cutting elements and powdered tungsten carbide and nickel with a copper-nickel-tin matrix in the manner described earlier. The tests were carried out by drilling in a sandstone formation with a conventional rotary rig and auxiliary equipment. A bit weight of 15,000 pounds and a rotary speed of 60 revolutions per minute were used. It was found that the matrix metal on the blades of the first bit rapidly fractured under the high stresses generated during the drilling operation. Measurements showed that the blades wore away at the rate of about 0.23 inch for each feet drilled. With the second bit, on the other hand, no fracturing of the matrix occurred. The blade wear rate was less than that with the first bit. The benefits due to the presence of carbide crystals in the matrix as a discontinuous phase are thus apparent.

This application is a continuation-in-part of Serial N 0. 128,591, Hard Surfacing Material, filed in the US. Patent Ofiice on August 1, 1961, by Harold C. Bridwell and David S. Rowley, and now abandoned.

What is claimed is:

1. An improved hard surfacing material comprising a plurality of closely-spaced hard metal carbide particle between about 0.045 and about 0.400 inch in size bonded together by a softer metal which melts at a temperature between about 1550 F. and about 2400 F. and in the molten state has the ability to wet said particles, said particles comprising tungsten carbide and said softer metal containing fine crystals of precipitated hard metal carbide as a discontinuous phase.

2. A hard surfacing material as defined by claim 1 wherein said carbide particles are particles of cemented tungsten carbide.

3. A hard surfacing material as defined by claim 1 wherein said softer metal is a copper-containing alloy.

4. A hard surfacing material comprising a plurality of closely-spaced tungsten carbide particles between about 0.045 and about 0.400 inch in size; an alloy bonding said carbide particles together, said alloy having a melting point between about 1550 F. and about 2400 F. and

9 in the molten state having the ability to wet said carbide particles; and a plurality of structurally-altered tungsten carbide powder granules and fine crystals of precipitated tungsten carbide dispersed within said alloy as a discontinuous phase.

5. A hard surfacing material as defined by claim 4 wherein said carbide particles are particles of cemented tungsten carbide.

6. A hard surfacing material as defined by claim 4 wherein said alloy is a copper-nickel alloy.

7. A hard surfacing material as defined by claim 4 wherein said alloy is an iron-nickel alloy.

8. A hard surfacing material comprising a plurality of closely-spaced cemented tungsten carbide cutting elements ranging between about 0.050 and about 0.250 inch in size; a copper-nickel-tin alloy bonding said cutting elements together, said alloy having a melting point between about 1550 F. and about 2400 F. and in the molten state having the ability to wet said cutting elements; and a plurality of structurally-altered tungsten carbide grains and precipitated tungsten carbide crystals present in said alloy as a discontinuous phase.

9. A process for the manufacture of a hard surfacing material which comprises the steps of dissolving a hard metal carbide powder comprising tungsten carbide in a molten matrix metal having a melting point between about 1550 F. and about 2400 F. and in the molten state having the ability to wet the hard metal carbide powder; alloying said molten matrix containing dissolved hard metal carbide powder with a plurality of closely-spaced hard metal carbide particles between about 0.045 and about 0.400 inch in size at a temperature between about 1750 F. and about 2500" F., said particles comprising tungsten carbide; and thereafter cooling said matrix metal and particles to effect a bond between said matrix metal and particles and precipitate fine crystals of hard metal carbide in said matrix metal as a discontinuous phase.

10. A process for the manufacture of a hard surfacing material which comprises the steps of dissolving a hard metal carbide comprising tungsten carbide in a molten matrix metal having a melting point between about 1550 F. and about 2400 F. and in the molten state having the ability to wet the hard metal carbide; placing hard metal carbide cutting elements between about 0.045 and about 0.400 inch in size in a refractory mold, said cutting elements comprising tungsten carbide; infiltrating said cutting elements in said mold with said matrix metal containing said dissolved carbide at a temperature between about 1750 F. and about 2500 F.; and thereafter cooling the contents of said mold to effect a bond between said matrix metal and cutting elements and precipitate fine crystals of hard metal carbide in said matrix metal as a discontinuous phase.

11. A process for the manufacture of a hard surfacing material which comprises forming an intimate mixture of hard metal carbide particles between about 0.045 inch and about 0.400 inch in size and hard metal carbide powder granules minus mesh in size in a refractory mold, said particles and granules comprising tungsten carbide infiltrating said mixture of carbide particles and powder granules in said mold at a temperature between 1750 F. and about 2500 F. with a molten matrix metal melting between about 1550 F. andabout 2400" F. and having the ability to wet said hard metal carbide particles and powder granules in the molten state, and thereafter cooling the contents of said mold to effect a bond between said matrix metal and said particles and powder granules and precipitate fine hard metal carbide crystals in said matrix metal as a discontinuous phase.

12. A process for the manufacture of a hard surfacing material which comprises the steps of forming an intimate mixture of tungsten carbide particles between about 0.045 and about 0.400 inch in size and powdered tungsten carbide and nickel minus about mesh in size in a refractory mold; infiltrating said mixture in said mold with a molten copper-nickel-tin alloy at a temperature between about 2000 F. and about 2250 F., said alloy having the ability to wet said carbide particles and powder in the molten state; and thereafter cooling the contents of said mold to effect a bond between said tungsten carbide particles and said alloy and precipitate fine tungsten carbide crystals in said alloy as a discontinuous phase.

13. A process as defined by claim 12 wherein said mixture of tungsten carbide particles and tungsten carbide powder is formed in contact with a steel tool surface in said mold.

14. A cutting tool hard surfaced with a material comprising a plurality of hard metal carbide cutting elements between about 0.045 and about 0.400 inch in size bonded together by a softer metal which melts at a temperature between about 1550 F. and about 2400 F. and in the molten state has the ability to wet said cutting elements, said hard metal carbide cutting elements comprising tungsten carbide and said softer metal containing powder granules and fine precipitated crystals of a hard metal carbide comprising tungsten carbide as a discontinuous phase.

15. A tool as defined by claim 14 wherein said softer metal is a copper-nickel-tin alloy.

References Cited in the file of this patent UNITED STATES PATENTS 2,201,150 Boyer May 21, 1940 2,201,151 Boyer May 21, 1940 2,833,638 Owen May 6, 1958 2,906,612 Anthony et al Sept. 29, 1959 

4. A HARD SURFACING MATERIAL COMPRISING A PLURALITY OF CLOSELY-SPACED TUNGSTEN CARBIDE PARTICLES BETWEEN ABOUT 0.045 AND ABOUT 0.400 INCH IN SIZE; AN ALLOY BONDING SAID CARBIDE PARTICLES TOGETHER, SAID ALLOY HAVING A MELTING POINT BETWEEN ABOUT 1550*F. AND ABOUT 2400*F. AND IN THE MOLTEN STATE HAVING THE ABILITY TO WET SAID CARBIDE PARTICLES; AND A PLURALITY OF STRUCTURALLY-ALTERED TUNGSTEN CARBIDE POWDER GRANULES AND FINE CRYSTALS OF PRECIPITATED TUNGSTEN CARBIDE DISPERSED WITHIN SAID ALLOY AS A DISCONTINUOUS PHASE. 